This invention relates to electric motors, and particularly electric motors whose electrically energized salient stator poles terminate in stator teeth that oppose rotor teeth on the rotor periphery, and in which permanent magnets located between adjacent stator teeth and/or rotor teeth and magnetized transverse to the stator-rotor gap enhance the motor torque relative to the applied ampere-turns.
Such electric motors are disclosed in the aforementioned U.S. applications. The enhancement described in these applications afford hybrid motors and variable reluctance motors substantial increases, such as 50%, in torque constant. Permanent magnets of materials such as samarium cobalt are located between the stator teeth of hybrid stepping motors, between the stator teeth and rotor teeth of some variable reluctance motors, and between only the stator teeth of other variable reluctance motors. These magnets increase the torque available from a given ampere-turns excitation by controlling the motor's air gap and altering the permeance slope, i.e. the torque making mechanism. The inter-teeth magnets also increase the rate of change of flux through the teeth when the motor rotates, thereby improving the motor's performance as a generator.
In the past, production of such motors has required placement of permanent magnet inserts in the slots between stator teeth and between rotor teeth. Such inserts are difficult to manufacture and the task of placing them and securing them in position has been laborious.